1. Field of the Invention
This invention relates to a drive control apparatus for a series hybrid vehicle (called "SHV" hereinafter), and more particularly to a drive control apparatus for controlling a motor to be installed in the SHV.
2. Description of the Related Art
A variety of hybrid vehicles (called "HV" hereinafter) having an engine and a driving motor as driving apparatuses have been proposed up to now. The HVs are roughly classified into parallel hybrid vehicles (PHVs) and SHVs. Usually, the SHV has a configuration as shown in FIG. 15.
In FIG. 15, the SHV includes an engine 10, a generator 12 and a motor 14. The generator 12 is a d.c. generator to be rotatably driven by the engine 10. The engine 10 and the generator 12 are mechanically connected via a speed increasing unit 16. The speed increasing unit 16 increases the number of rotations of the engine 10 so as to be compatible with the generator 12.
The generator 12 supplies its output to the motor 14 via an invertor 18, which converts the received output into 3-phase a.c. electricity, and provides it to the motor 14. The motor 14 is a 3-phase a.c. motor, of which mechanical output is transmitted to wheels 24 via a differential gear 22 and so on.
The invertor 18 also receives d.c. electricity from a main battery 26. In other words, the motor 14 can be selectively driven by the electricity either from the generator 12 or the battery 26. For instance, when the engine 10 is inoperative, the generator 12 cannot supply the electricity to the motor 14, so that the motor is driven by the electricity solely from the main battery 26. Since the main battery 26 is a chargeable and dischargeable type, it can be charged by a regenerated power from the motor 14, a charger (not shown), or the like. The main battery 26 can supply the electricity to electric appliances mounted on the vehicle via an auxiliary battery.
The engine 10, generator 12, invertor 18 and other units are controlled by an electronic control unit ECU 28. Specifically, the ECU 28 controls the operation of components of the vehicle such as fuel injection into the engine 10, excitation of the generator 12, and the switching of transistors in the invertor 18 using a pulse width modulation (PWM) signal. For instance, the ECU 28 receives a signal indicating the extent of a driver's stepping on an accelerator or brake pedal. Based on the signal, the ECU 28 controls a speed of the engine 10 and an excitation voltage of the generator 12, providing the invertor 18 with the PWM signal, and controlling the vector of a primary current of the motor 14.
With the foregoing SHV, the motor 14 is selectively driven by the electricity either from the generator 12 or the main battery 26.
Selection of either the generator 12 or the main battery 26, or use of both of these power sources depends upon the acceleration performance or other factors of the vehicle so as to satisfy the desired specification. For instance, it is preferable to set up a power supplying plan in which only the generator 12 is used to supply an output in a given range.
Up to now, PHVs in which either an engine or a battery, or the engine and battery is selectively used as a drive source are known (refer to Japanese Patent Publications Sho 62-27603 and Sho 62-27604). By using the techniques disclosed in these references, it is possible to control the supply of power for the SHV.
With the prior art, selection of the drive sources is mechanically performed, which causes undesirable shocks at the time of selection.